1. Field of the Invention
The present invention is in the field of orthodontics and more specifically is a removable orthodontic appliance that employs vertically-indexed posterior bite plates for correcting Class II Division 1 malocclusions primarily.
2. The Prior Art
An appliance known as the U-bow activator of Karwetzky has been used to correct Class II Division 1 malocclusions and certain other malocclusions. The appliance, shown in FIG. 1, consists of maxillary and mandibular active plates, 1 and 2 respectively, joined by two U-bows 3, 4 of heavy wire. The plates cover the occlusal surfaces of all the teeth as well as parts of the gums and touches the tongue along their lingual aspects. The position of the lower plate relative to the upper plate is controlled by the U-bow and the lower plate is moved forward relative to the upper plate by squeezing the sides of the U-bow together.
Far from having indexing planes comparable to those of the present invention, the Karwetzky appliance has smooth planar horizontal opposing surfaces on the upper and lower plates.
Because the wire used in forming the U-bow must be stiff enough to oppose any tendancy of the lower jaw to move posteriorly, the wire and the plates themselves tend to be bulky. Patient adaptation to this appliance is difficult, and while it is being worn normal speaking and eating activities are impossible.
Full time wear is impossible. Sometimes, when the patient attempts to sleep with the appliance in place, the mandibular teeth will drop behind the mandibular plate thereby rendering the device ineffective.
In the Karwetzky appliance, unlike the present invention, when the lower jaw tries to move posteriorly, it pulls the connected plates posteriorly, and this tendancy is opposed mainly by the maxillary anterior teeth which are thereby moved distally. This is undesirable because those teeth are the least able to withstand such a force. In contrast, in the appliance of the present invention, the posterior pulling of the lower jaw is opposed mainly by the upper posterior teeth which are more able to withstand the force.
Another appliance sometimes used for correcting Class II Division 1 malocclusions is known as the Schwartz double plate. This appliance, shown in FIG. 2, includes a lower plate 5 that fits behind the incisors 6. This lower plate includes a distal surface 7 that slopes downwardly posteriorly. The upper plate 8 fits behind the upper incisors 11 and includes a downwardly and distally extending portion 9 that lies behind the rear surface of the lower plate. The front surface 10 of this downwardly and distally extending portion slides along the posterior surface 7 of the lower plate. As the lower jaw is closed, it is forced forward as the inclined distal surface 7 of the lower plate rides up along the downwardly and posteriorly extending portion 9 of the upper plate. In a preferred embodiment of the double plate, the downwardly and posteriorly extending portion 9 of the upper plate is replaced by adjustable guide elements formed of wire.
An obvious defect of this type of appliance is that as the mandible opens, as in sleep, the lower plate 5 slides downwardly and posteriorly along the upper plate thereby rendering the appliance ineffective during sleep. Also, the patient cannot eat or speak normally with the appliance in place.
In contrast to the appliance of the present invention, in the double plate appliance, the main force is applied against the lower incisors, tending to tip them forward.
In summary, none of the appliances of the known prior art is fully satisfactory, and the need for an improved appliance was recognized by the present inventor.